Comitology is an important part of the EU’s regulatory framework. Hence, lobbying by outside interests is to be expected. However, lobbying in the comitology system has received almost no scholarly attention. This paper provides the first understanding of the subject by analysing the access of business interests to actors in the comitology system. The analysis is designed as a most likely study of two cases, aviation safety and CO2 quotas. Based on Bouwen’s rationalist theory of access goods, the empirical analysis shows that lobbying is prevalent, especially by sectoral interests providing expert knowledge and targeted mainly at the Commission, but also at the member states in the comitology committees, and the European Parliament. The case studies therefore indicate that lobbying is widespread in the comitology system and important to study in order to understand the outputs from this part of the EU political system.